Retrofit window replacement is the most common project Lion handles across West LA — and also the one homeowners have the most questions about. Unlike new construction, retrofit windows install into an existing, occupied home, which changes what the day of installation actually looks like.

This guide walks through what to expect from the first measurement appointment to the final walkthrough, so there are no surprises once the crew arrives.

What "Retrofit" Actually Means

A retrofit window (sometimes called a "block frame" or "insert" window) is designed to install into the existing window opening without disturbing the exterior stucco, siding, or trim. The old window frame is removed, but the surrounding wall stays intact. This is different from a nail-fin new-construction window, which requires removing exterior finish material down to the sheathing.

For occupied homes, retrofit is almost always the better fit — it's faster, creates less exterior disruption, and avoids re-finishing work that can add days and cost to a project.

The best retrofit installs are the ones where you'd never guess a crew was in the house — clean lines, no exterior patchwork, and daily cleanup that leaves no trace.

Before the Install: Measurement and Ordering

Once an estimate is accepted, Lion schedules a professional measurement visit. This is where exact frame sizes, sill conditions, and any structural concerns are documented. This step typically happens one to two weeks before the crew arrives, and it's credited toward the final project cost.

  • Exact opening measurements for every window being replaced
  • Sill and header condition check for water damage or dry rot
  • Confirmation of material, operating style, and glass package
  • A written, itemized quote before any product is ordered

Lead time from order to delivery is typically four to eight weeks depending on the manufacturer and configuration — this is the single biggest variable in a retrofit project's overall timeline.

Interior view of a finished retrofit window installation in a West LA living room
A completed retrofit installation — the surrounding stucco and trim remain untouched.

Installation Day: What Actually Happens

For a typical whole-home project (10–20 windows), most crews complete the work in one to two days. Here's the general sequence for each opening:

  1. Interior and exterior areas are protected with drop cloths and plastic sheeting.
  2. The old window sash and frame are carefully removed.
  3. The opening is inspected and, if needed, prepped for any minor repairs.
  4. The new retrofit window is set, leveled, and fastened into the existing frame.
  5. Exterior and interior sealant is applied for a weathertight finish.
  6. Interior trim is reset, and the area is cleaned before the crew moves to the next opening.

Expect some noise from removal and minor drilling, and expect the work area to be roped off for safety — but a well-run crew cleans up daily, so the home is livable throughout the project, not just at the end.

After Installation: What to Check

Before the crew leaves, walk through each opening with them. Look for:

  • Smooth operation — the window opens, closes, and locks without resistance
  • Clean, even sealant lines on both interior and exterior
  • No visible gaps between the new frame and the existing wall
  • Trim and the surrounding wall finish remain intact

Manufacturer warranties on the product typically run 10–20 years depending on the line, and Lion's installation labor is separately warrantied — ask for both in writing before the crew leaves the site.

Ready to start?

Send photos or a rough opening count through Lion's guided estimate tool — we'll come back with a considered number.

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